This invention relates to a controller for a rivetting machine which makes it possible to carry out rivetting automatically by simply inputting data of machining characteristics.
A rivetting machine is known which comprises a motor-driven spindle extending through and journaled to a piston shaft of a hydraulic cylinder connected to a hydraulic power source, and a rivet head forming tool having a forming shaft and secured to the bottom end of the spindle. The spindle is lowered by extending the hydraulic cylinder to press the bottom end face of the forming shaft against the top end face of a work rivet by the hydraulic force acting on the piston shaft and at the same time the spindle is rotated by the motor. Thus a rivet head is formed on the work rivet.
Since the work rivets placed on the work table are of various heights according to the products to be formed, it is necessary to adjust the length of the stroke of the hydraulic cylinder. For this purpose, a mechanical stroke adjusting structure was used. Such a structure may be a stopper plate provided around the piston shaft of the hydraulic cylinder so that its vertical position will be adjustable by use of an index motor or the like. In this arrangement, the lower limit of the stroke of the piston shaft is set by abutting a member fixed to the piston shaft against the stopper plate when the piston shaft is moved down. Also, such a structure may comprise a disc member provided around the piston shaft and having stopper pins of different heights protruding upwardly therefrom, and a plate-like member integral with the piston shaft and provided with a pin extending downwardly. As the piston is lowered, the pin at the side of the piston shaft will abut one of the stopper pins selected by turning the disc member. Thus the lower limit of the stroke of the piston shaft is set.
In order to position a work rivet with respect to the forming shaft by moving a work table a plane (X-Y plane) perpendicular to the hydraulic cylinder in X-Y directions relative to the forming tool, a manual or motor-driven ball screw type table moving mechanism was used.
But the above-described prior art mechanical stroke adjusting structure not only required extra parts such as an index motor and stopper means but the stroke adjustment was very troublesome. These problems have been big obstacles to full automation of rivetting work. Also, since a stepless adjustment of the stroke was difficult, a special stopper had to be prepared when forming an off-specification work rivet. This incurs extra labor and costs.
Further, the ball-screw type mechanism for moving the X-Y table has a problem in that its moving speed is slow. If the moving speed is increased, the positioning accuracy worsens. Further, since wear on the ball-thread can also lower the positioning accuracy, frequent lubrication and exchange of parts are necessary. This also increases the cost.
Further, the setting of caulking pressure had to be carried out by manually adjusting the working pressure of the relief valve according to the diameter of each rivet and its material. This is also troublesome and has been another obstacle to the automation of rivetting work.